RELATIONSHIP OF BLOOD CORTICOSTERONE, IMMUNOGLOBULIN AND HEMATOLOGICAL VALUES IN YOUNG CROCODILES (CROCODYLUS-POROSUS) TO WATER TEMPERATURE, CLUTCH OF ORIGIN AND BODY-WEIGHT

Objective To examine whether sub-optimal temperature induced stress an d immunosuppression in farmed saltwater crocodile (Crocodylus porosus) hatchlings. Design A clinico-pathological study. Animals A total of 1 40 hatchlings were used. Procedure Body weight and length, plasma cort icosterone and immunoglobulin concentrations and total and differentia l white blood cell counts were measured in 140 hatchlings from five cl utches divided between five water temperature treatment groups, Initia lly all groups were housed at 32 degrees C for 10 weeks, then two grou ps (L, LC) were changed to low temperature (28 degrees C) and two grou ps (H, HC) to high temperature (36 degrees C), while one group (C) rem ained at 32 degrees C. The LC and HC groups were maintained at these t emperatures for 10 days, after which the water temperature of both gro ups was returned to 32 degrees C. Blood samples were collected twice ( at 6 and 9 weeks of age) before the initial temperature change, and at 10 days and 4 weeks after the initial temperature change (at 11.5 and 14 weeks of age), Results Except for an increase in plasma corticoste rone in the HC group and a decrease in the L group when the temperatur e change was first introduced, changes in plasma corticosterone were n ot significant, There were no significant changes in immunoglobulin co ncentrations. There were, however, significant decreases in the total white cell and lymphocyte counts in the LC group after the temperature was decreased to 28 degrees C, and an increase in these counts after water temperature was returned to 32 degrees C. Clutch of origin had s ignificant effects on body weight and length gains, and there were neg ative relationships between body weight and corticosterone concentrati ons and between body weight and immunoglobulin concentrations. Conclus ions As haematological changes indicative of stress were not associate d with significant changes in serum corticosterone, immunosuppression in young crocodiles may be independent of the hypothalamic-pituitary-a drenal cortical axis.